test: add unit tests for utility modules

[Tyrrnien81]

Summary

• Add tests/unit/ directory with unit tests for ros_mcp/utils/
• Cover response.py, config_utils.py, network_utils.py
• All network operations are mocked — no real connections needed
• Total: 47 test cases covering all code branches and edge cases

Motivation

Currently, the only tests in tests/ verify package installation (Docker-based). There are no tests for the core utility logic that every tool depends on. This PR adds foundational unit test infrastructure.

Changes

File	Purpose
tests/unit/__init__.py	Package init
tests/unit/conftest.py	Shared fixtures (rosbridge responses, robot YAML configs)
tests/unit/test_response.py	20 tests for response validation functions
tests/unit/test_config_utils.py	12 tests for robot config loading and listing
tests/unit/test_network_utils.py	15 tests for DNS resolution and ping diagnostics

Test Plan

• uv run pytest tests/unit/ -v — all 47 tests pass
• uv run ruff check . — lint passes
• uv run ruff format --check . — format passes
• No changes to existing source code — tests only
• No overlap with integration tests in refactor(detection): ROS version detection with RosVersion enum, add tool tests (step0) #276-refactor(topics): migrate to rosapi_service()/rosapi_type(), add tool tests (step3) #281

Closes #308

[samkwak188]

I read all five files under tests/unit/. The suite cleanly targets ros_mcp/utils (response, config_utils, network_utils) with shared fixtures in conftest.py and mocked I/O so nothing requires a live network or robot. Structure and naming look consistent with pytest usage; author’s test plan (pytest tests/unit/, ruff) matches the intent for #308.

[raphy0316]

Looks great overall — test structure and coverage are really solid
Nice use of mocking and good edge case handling.

Just a couple small thoughts:

• Might be safer to use exact matches instead of substring checks for status
• test_with_real_robot_specs feels a bit like an integration test — maybe worth separating or marking later
• Monkeypatching __file__ works, but could be cleaner with injection if we refactor in the future

Otherwise, looks good to me

[stex2005]

Thanks for putting this together, @Tyrrnien81! Great to see unit test infrastructure being built out, and the test organization is clean.

I've been working on the integration test suite (PRs #276-#281, #316, #321) and wanted to share some thoughts on how these two efforts overlap and where to focus energy.

What's most valuable here

The config_utils tests are the highlight — load_robot_config, get_verified_robot_spec_util, get_verified_robots_list_util have zero coverage elsewhere, and the tmp_path/monkeypatch approach is the right way to test them. That said, these are tightly coupled to the folder structure (Path(__file__).parent.parent.parent / "robot_specifications"), so the monkeypatching is inherently fragile. Worth keeping, but worth acknowledging in comments.

Where there's overlap

The response.py and network_utils.py tests overlap significantly with the integration test suite:

• _check_response and _safe_get_values are 3-line utility functions. The integration tests exercise them implicitly on every tool call (get_nodes, get_services, subscribe_once, etc.) — across 4 ROS distros with real rosbridge responses. Testing them 13 different ways with None/empty-dict/string/list inputs is testing Python dict behavior more than application logic.

• ping_ip_and_port has 12 fully-mocked tests, but tests/integration/test_connection.py already tests ping_rosbridge, ping_closed_port, ping_multiple_targets against real sockets — which catches real bugs that mocks can't.

• _resolve_dns tests that "127.0.0.1" returns itself — that's testing Python's ipaddress module, not our code.

Suggestion

Would you consider splitting this into smaller PRs?

1. PR 1: test_config_utils.py + conftest.py + __init__.py — this is the valuable, non-overlapping part. Merge it first.
2. PR 2 (optional): test_response.py — trimmed down to just the edge cases that integration tests don't cover (if any remain after review).
3. Skip test_network_utils.py — the integration tests cover ping_ip_and_port better with real sockets, and _resolve_dns is a thin wrapper around stdlib.

This keeps the test suite lean and avoids maintaining mock-heavy tests that duplicate what the integration suite already validates end-to-end.

Again, appreciate the effort here — especially the clean pytest structure and proper use of tmp_path fixtures! 🙏

[stex2005]

as per the comment above.